Tension release mechanism for sewing machines



Aug. 28, 1962 5. J. KETTERER TENSION RELEASE MECHANISM FOR SEWINGMACHINES Filed Aug. 24, 1961 INVENTOR. STANLEY J. KETTERER BY ,2 7ATTORNEY WITNESS rates Patented Aug. 28, 1962 This invention relates tolock stitch sewing machines of the type in which locking or bobbinjtbread is replenished automatically during a continuation of the sameinterrelated motion of the needle and the looptaker as is required forthe formation of lock stitches, and more particularly to a novel meansfor rendering inelfective the locking or bobbin thread tensioning meansduring the thread replenishing operation.

It is an object of this invention to provide a means for releasing theunder or bobbin thread tensioning means during introduction andreplenishment of a thread on a bobbin in place in a loop-taker so as toprovide for the smooth'flow of thread thereto with a minimum of stressthus reducing the possibility of thread breakage.

t is also an object of this invention to provide a novel under or bobbinthread tension releasing means which is compact, simple, and economicalin construction and which does not interfere with the operation of thethread replenishing mechanism.

In the accompanying drawing of a preferred embodiment,

FIG. 1 represents a vertical cross-sectional view of a sewing mechineloop-taker having this invention applied thereto and including afragment of the work support and the needle and illustrating therelative position of parts during introduction and replenishment ofbobbin thread,

FIG. 2 represents a vertical cross-sectional view of a sewing machineloop-taker similar to FIG. '1 but illustrating the relative position ofparts during the subsequent sewing operation,

FIG. 3 represents a-front elevational view of the looptaker of FIGS. 1and 2,

FIG. 4 represents a top plan View of the. bobbin case, and,

FIG. 5 represents a perspective View of the thread tensioning spring ofthis invention.

This invention is an improvement of the construction disclosed in thecopending United States patent application of Stanley J. Ketterer andWilliam J. Edwards, Serial No. 15,955, filed March 18, 1960. Thiscopending application may be referred to for the details of constructionof the loop-taker, particularly with regard to the means for introducingand replenishing a supply of under or looking thread to the bobbin andthereafter forming a lock stitch using the replenished bobbin threadsupply.

In the accompanying drawing, the sewing machine work support, asindicated at 11, is fitted with a throat plate 12 having an aperture 13through which passes an endwise reciprocable thread carrying needle 14.I ournaled beneath the work support is a hollow loop-taker drive shaft15 to which is fixed a loop-taker indicated generally as 16. Theloop-taker is formed with a cupshaped body portion 17 formed with a gap18 and at one side of the gap with a needle loop seizing beak 19. Thecup-shaped body portion of the loop-taker is formed internally with anannular raceway 20 in which is journaled by means of a bearing rib 21, abobbin case 22. The bobbin case is formed with a notch 23 whichaccommodates a rotation restraining finger 24 fixed relatively to theWork support, thus to prevent rotation of the bobbin case with respectto the looptaker. The'bobbin case 22 is formedwith a stud 25 disposedsubstantially co-axially of the loop-taker drive shaft 15 and internallythreaded to accommodate a headed screw 26. Journaled freely on the stud25 is a bobbin member 27 which is constrained for limited slidingmovement axially of the stud by the headed screw 26.

The loop-taker is preferably operated in timed relation with the needletwo revolutions for each needle reciprocation and in a timedrelationship such that the loop-taker beak 19 will pass adjacent to theneedle during each work penetration thereof for seizure of needle threadloop whenever a loop of thread is presented by the needle. Suchinterrelated motion of the needle and loop-taker is termed stitchforming motion and it will be understood that the same stitch formingmotion of the needle and loop-taker occurs during bobbin threadreplenishment even though no stitches will be formed during thereplenishing period.

Referring to FIG. 4, a gap 39 is formed in the bobbin case bearing rib21 providing an ingoing pocket 31 on that side of the gap toward whichthe loop-taker turns, against which pocket loops of thread seized by thelooptaker beak 19 are directed in the normal handling of thread loops bythe loop-taker. During the sewing operation when a free space existsbehind the bobbin and bobbin case as illustrated in FIG. 2, the loops ofthread which are carried into the ingoing pocket by the hook beak arefree to slide about the bobbin case,

one limb across the exposed face and one limb through the free spacebehind the bobbin case. During sewing, the portion of the loop which isinitially trapped in the ingoing pocket thus gradually slides across thegap 30 in the bobbin case hearing rib and is positioned at the oppositeside of the gap 30, which is termed the outgoing pocket 32, as thethread is drawn from the loop-taker and set into the work.

Referring to FIGS. 1 and 2, 40 indicates a bobbin.

winding member carried within the cup-shaped looptaker body andinterlocked for rotation with the looptaker. The bobbin winding memberis fast on a rod 41 shiftable axially Within the hollow loop-taker driveshaft 15. By means of a control mechanism (not shown) which may be inthe form of a cam means as described in the above referenced patentapplication No. 15,955, the rod 41 maybe shifted to position the bobbinwinding member into engagement with the bobbin member 27 as illustratedin FIG. 1, in which position thread wili be replenished on the bobbin.After the bobbin thread supply has been replenished, the rod 41 shiftedto the right as viewed in FIG. 2 to shift the bobbin winding member awayfrom the bobbin member thus readying the loop-taker for the formation ofstitches.

A leaf spring 42 carried on the loop-taker body portion extends inspaced relation behind the loop-taker beak 19 and is engaged by a threadgripping arm 43 on the bobbin winding member 49 when the bobbin threadis to be replenished so as to grip on the hook a loop of needle threadseized thereby. The bobbin winding member is formed with a rim 44 which,as illustrated in FIG. 1, envelops the bobbin member when the bobbinwinding member is shifted into engagement therewith. The movement tothe. left of the bobbin winding member during bobbin threadreplenishment shifts the bobbin member axially along the stud 25 asillustrated in FIG. 1, and a pin 45 on the bobbin Winding member engagesa notch 46 in the bobbin member to provide for a positive drive of thebobbin member.

When the bobbin winding member is shifted into the position illustratedin FIG. 1 for replenishment of the bobbin thread supply, the free spacebehind the bobbin case is closed, andthe thread loop carried by'the loopextremity of 'the thread tensioning spring is biased against one wall ofthe limb 51 of the thread accommodating slot as illustrated in FIG. 2 soto apply a frictional resistance to the passage ofthread to or from thebobbin to the work. A finger 55 is formedon the free extremity 54 of thethread tensioning spring, which finger extends, as illustrated in FIGS.1, 2 and 3, into the axial projection of the bobbin member 27 such thatupon axial sliding movement of the bobbin along the stud 25 when engagedby the bobbin winding member 40, the bobbin member will engage thefinger 55 and shift the thread tensioning spring away from that edge ofthe thread guiding slot toward which it is biased. a With thisIconstruction, therefore, during introduction and replenishment of threadto the bobbin, the bobbin thread 'tensioning means will be renderedineffective and the smooth flow of thread thereto will be unimpeded,thus minimizing the possibility of thread breakage. The tension will beautomatioally reapplied when the parts "are shifted into position forsewing.

f In FIG. 1, in which the parts are illustrated in a position for bobbinthread replenishment, the loop-taker beak 19 is illustrated in aposition in which it has seized a loop of needle thread T. The bobbinthread tensioning spring5'3, as illustrated in this figure, is held inan ineffective position for introduction and replenishment of the bobbinthread free of any efiect of the tensioning means. 7

In FIG. 2, the loop seizing beak 19 of the loop-taker is similarlyillustrated in a position seizing a loop of needle thread 'I and thethread which had previously been replenished on the bobbin is indicatedat T under the influence of the bobbin thread tensioning spring 53. jHaving thus setforth the nature of this invention, what I claim hereinis: o

1. A look stitch sewing machine, having a frame'ineluding a worksupport, an endwlise reciprocatory thread carrying needle carried bysaid frame at one side of-said work support, a loop-taker journaled forturningmovementin the frame at the opposite side of said work support,means for imparting interrelated motion to said' needle and saidloop-taker as is required for the formation of lock stitches, a bobbincase journaled in said loop-.taken'meaus carried on said frame forconstraining taker, a bobbin journaled in said bobbin ease for turningand axially sliding movement therein, a

thread tensioning spring anchored on said bobbin case and having a freeextremity biased yieldingly against said bobbin case, means eflectiveduring said interrelated motion of said needle and loop-taker as isrequired for the formation of lock stitches for introducing a threadbetween the free extremity of said thread tensionspr-ing and said bobbinease and to said bobbin, bobbin winding means including a bobbinrotating member shiftable in adireotion axially of said bobbin intoeliective driving engagement therewith and effective during continuedinterrelated motion of said needle and loop-taker as is required for theformationof lock stitches for winding on said bobbin said threadintroduced thereto, and

means operated by said bobbin winding means for hi n he r e r i o Said'h ead e i ng spring away from said bobbin case during operation of saidmeans for introducing thread to said bobbin and during operation of saidbobbin winding means.

2, A mechanism as set forth in claim 1 in which said means for shiftingthe free extremity of said thread tensioningspring away from. saidbobbin case comprises a finger carried by said thread tensioning springand disposed in the path of axial sliding movement of said bobbin attheopposite side ofsaid bobbin from said bobbin rotating member. 1 I r V 3.A loop-taker for a lock stitch sewing machine'com: prising a rotatablecup-shaped loop-talker body formed with a gap, a loop seizing beakcarried by said looptaker body and projecting into said gap in thedirection of rotation of said loop-taker body, said looptaker body beingformed with an annular internal groove defining a raceway, anon-rotating bobbin case formed said bobbin case from turning movementwith said loopwith a cavity, a bearing rib formed on said bobbin caseand journaled in the raceway in said loop-taker body, said bear-ing ribbeing formed with a gap, one, edgeof said gap in said bobbin casebearing rib toward which said loop-taker body rotates defining aningoing threadv pocket, at bobbin journaled in said bobbin case forturn:

ing and limited axial sliding movements therein, a thread guiding slotformed in said bobbin case open to said bobbin case cavity and leadingfrom said ingoing pocket, a thread tensioning spring means carried bysaid bobbin case and yieldingly bearing against one wall of said threadguiding slot, and a finger formed on said thread tensioning spring meansand extending nto the path of axial sliding movement of said bobbin forshifting said thread tensioning spring means away from said one wall ofsaid thread guiding slot upon axial shifting of said bobbin. Y

References Cited in the file of this patent UNITED STATES PATENTS1,224,744 France Feb, 8, 1960

